Materials · Specified by duty

Fresh stock.
Traceable properties.

The dry-air rig, cold recuperator and hot-side core need different material systems. The proposed build specification calls for fresh, traceable stock and records for its joining and heat treatment.

Candidate directions, not a released bill of materials
ComponentMaterial directionWhat the next build must qualify
Dry-air manifold and supports6061-T6 aluminiumMachining, joints, stiffness and installed leakage
Cold counterflow coreBrazed aluminium plate-fin concept; 3003-family property screenActual alloy/temper, brazing, conductance, pressure loss and thermal gradients
Cold linework and interfaces316-family stainless conceptExact grade, weld condition, contraction, seals and heat leakage
Separate 700 K hot-side branchAlloy 625 tube/plate conceptCore construction, thermal stress, pressure fatigue, joining and installed mass

Give the cold joints room to move.

The NIST property fits predict about 1.88 mm contraction for a 500 mm 6061-T6 part cooled from 293.15 to 90 K, versus about 1.35 mm for 316 stainless. The roughly 0.53 mm difference becomes a requirement for sliding supports or suitable compliant interfaces.

These are property-fit estimates for a cold component, not a vehicle-body cooling or tyre-grip claim. Actual temperature gradients and joint loads still need a structural solution.

Keep the temperature ranges separate.

The cryogenic property fits stop near room temperature. They are not extrapolated to the 700 K heat-source study.

Industrial brazed-aluminium exchangers support the cold-core technology choice. Alloy 625’s published temperature range supports a separate hot-side candidate; it does not qualify the proposed core or its welds.

Property calculations and coefficients ↗NIST: 6061-T6 ↗NIST: 316 ↗Chart: cryogenic exchanger technology ↗Alloy 625 manufacturer data ↗